In a system on chip (SOC) application, the system dynamically powers down unused sections and powers up those sections when they are accessed. In some circuit designs, when a section is not active (e.g., powered down), a header or a footer circuit is used to cut off the leakage paths from a high voltage power supply VDD or a low voltage power supply VSS, respectively.
A conventional header circuit turns on the power directly. If the chip is relatively big, the current required to turn on a large portion of the chip may lower down the power supply voltage level and cause problems. For example, other logic sections in operation may functionally crash and an analog block's accuracy may be affected due to the lower voltage level.
In another example, a high peak turn-on current may induce an electromigration (EM), which is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms, potentially causing unsound structure due to undesirable material loss.
Accordingly, new mechanisms are desired to solve the above problems.